Interestingly, in all cases, the mutant RB1 allele frequency was shown to be >90% in the cfDNA where one allele of RB1 remained (LOH cases) or >45% where two RB1 alleles (one mutant and one wild type) were present, suggesting that >90% of the cfDNA present in AH of enucleated eyes is of tumour origin. The gene discussed is RB1; the disease is neoplasm.